textproduct: Albany

UPDATE

As of 635 PM EST, rain and embedded thunderstorms tracking eastward across Mohawk Valley and eastern Catskills and approaching the Capital Region. Overall tendency has been for CG lightning to decrease as forcing outruns best instability, however we have increased coverage for slight chance of thunder as far east as I-87 through this evening.

Thunderstorms earlier were producing rainfall rates as high as 1"/hour across central NYS per NY Mesonet, but have trended down to ~0.35"/hour or less. Still, some brief heavy downpours and rumbles of thunder will remain possible for areas mainly west of I-87 and near/south of I-90 for the next 1-2 hours. We did have one report of less than pea-size hail near West Winfield in southern Herkimer County shortly before 6 PM with stronger storm earlier.

Temps have dropped to around freezing across portions of the southern Adirondacks, and expect areas of freezing rain to occur within the advisory area.

SYNOPSIS

Low pressure moving across northern New York will bring precipitation this evening into Sunday. Parts of the southern Adirondacks, Upper Hudson Valley and southern Vermont will see freezing rain. Elsewhere, rain is expected. Additionally, the western Mohawk Valley and the eastern Catskills may get a rumble of thunder. Behind the storm, chilly and blustery conditions then arrive for Sunday through Monday with lake effect and upslope snow showers.

SHORT TERM /THROUGH SUNDAY NIGHT/

Key Message:

- Moderate to high confidence in a period of freezing rain late this afternoon into tonight for parts of the Adirondacks, Upper Hudson Valley and southern Vermont. A Winter Weather Advisory is in effect for these areas starting between 4 PM and 7 PM today through 1 AM tonight.

- Increasing confidence for gusty winds and lake effect/upslope snow showers Sunday through Monday which can result in reduced visibility. There is a 50 to 90% chance for 24 hour maximum wind gusts Saturday night through Sunday night to exceed 40mph mainly down the Mohawk Valley, Greater Capital District into western MA.

Discussion:

Surface Low pressure over the upper Great Lakes will is forecast to move southeast to north of Lake Ontario by late this evening and then eastward to the Maine Coast by Sunday morning. The system is associated with a deepening 500mb short wave moving southeast from central Canada. Warm air and moisture advection ahead of the sfc warm front has allowed a precipitation shield to develop over western and central NY with some embedded thunderstorms. Thunderstorms are related to elevated cape. As the storm moves eastward, the steep mid level lapse rates look to get pinched off reaching to the western and southwestern parts of the forecast area. Best chance for any rumbles of thunder look to be across the western Mohawk Valley and the eastern Catskills.

The leading edge of the precipitation shield reaches western areas around sunset and given dry air noted on forecast soundings in the 925 - 800hPa layer, wet-bulbing processes will cool the column. While most areas will be mild enough to support plain rain, sfc temperatures in the southern Adirondacks and parts of the Upper Hudson Valley and southern Green Mountains likely cool towards or even a few degrees under freezing as precipitation begins, supporting freezing rain. After this initial drop in temperature at the start of the precipitation, temperatures are forecast to gradually rise overnight to above freezing all areas. Total ice from freezing rain still expected to range from a light glaze up to tenth of an inch or so (highest amounts across the highest terrain of the southern Adirondacks and southern Greens) as the short duration of cold air should limit ice accretion amounts.

The warm sector is quite impressive with a notable 40-50kt jet in the 900-800hPa layer directing a moisture rich and mild plume into the Northeast with PWATs nearing 1" and 850hPa isotherms +6C to +9C. Expecting this moisture rich and dynamic system to produce a period of steady rain through about 06 UTC before the best forcing exits to our east.

By sunrise Sunday expecting a sharp wind shift to the west- northwest as the cold front swings through the Northeast before sunrise. Strong push of cold air advection combined with a tightening sfc pressure gradient will support a well-mixed boundary layer and blustery winds with temperatures falling through the day. In fact, latest probabilistic guidance from the NBM shows a 40 to 90% chance for 24 hour maximum wind gusts Saturday night through Sunday night to exceed 40mph with the highest values focused down the Mohawk Valley, Greater Capital District into western MA due to channeled flow. There is a low chance that we will need wind advisory for these areas mainly for the daytime on Sunday.

Besides the gusty winds, the incoming cold air mass will lead to a lake effect and upslope snow response. Guidance suggests the potential for a multi-lake connection with single lake effect bands extending well inland off Lake Ontario. The west-northwest flow direction should keep the lake bands mainly south of I-90 and directed more into the northern and eastern Catskills. Some bands can even extend into parts of Hudson Valley and as far east as western New England. Even without any lake bands, the strong westerly flow will likely support upslope snow along the spine of the Greens and the Taconics. Latest NBM probabilistic guidance limits 2"+ snow amounts to the western Adirondacks (mainly near and north of Route 28) but the exact placement and duration/intensity of any lake band will determine snow amounts, especially Sunday afternoon and evening when inversion heights rise and the column turns cold enough to support snow accumulations for areas outside of higher elevations. The gusty winds will likely result in reduced visibility during any snow.

LONG TERM /MONDAY THROUGH SATURDAY/

Lake effect and upslope snow looks to continue into Monday owing to cold, moist cyclonic flow. Chilly temperatures and gusty winds continue as well. Although 850mb temps gradually rise and a drier more anticyclonic flow begins to build in on Tuesday, there may still be some snow shower activity over the western Mohawk Valley and southwestern Adirondacks as the flow remains off of Lake Ontario.

Subsidence finally builds overhead Tuesday night into Wednesday as the trough gradually exits to our east and sfc high pressure builds in. This will support drier weather heading into the middle of the week and temperatures remain slightly cooler than normal. Milder unsettled weather looks to return for the end of the week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Area of rain continues to track east ahead of a warm front. There could be a few thunderstorms impacting KALB over the next hour, otherwise mainly a period of moderate rain with VFR/MVFR Cigs/Vsbys. Rain should taper off from west to east between 04Z-07Z/Sun, however MVFR/borderline IFR Cigs will likely continue until a cold front tracks through between 10Z-13Z/Sun. After 13Z/Sun, Cigs should become mainly VFR. However, scattered afternoon snow showers may produce intermittent MVFR/IFR Vsbys/Cigs in the afternoon, especially at KPSF.

South to southeast winds overnight at 4-8 KT will become southwest to west around daybreak and increase to 8-14 KT with gusts of 20-25 KT, then becoming west to northwest at 10-20 KT with gusts of 25-35 KT from late morning through sunset. Low level wind shear will also be likely for a period late tonight as surface winds remain light from the south to southwest at 5-10 KT while winds around 2000 FT AGL increase from the west to 30-35 KT.

Outlook...

Sunday Night: Moderate Operational Impact. Breezy. Chance of SN. Monday: Moderate Operational Impact. Windy With Gusts To 30 kts. NO SIG WX. Monday Night: Low Operational Impact. Breezy. NO SIG WX. Tuesday: Low Operational Impact. Breezy. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory until 1 AM EST Sunday for NYZ033-041- 042-082-083. MA...None. VT...Winter Weather Advisory until 1 AM EST Sunday for VTZ013-014.